Device for exchanging data and process for operating it

ABSTRACT

A device or arrangement for exchanging data between a main station (master) ( 10 ) and at least one secondary station (slave) ( 12, 12   n ), which each have access to at least one common data line ( 11 ) via interfaces CAN, and processes for operating the device. Except for an individual identifier (a, b, . . . , d) of each slave ( 12, 12   n ), which is stored in an identifier memory ( 27, 27   n ) disposed in the slave ( 12, 12   n ), the slaves ( 12, 12   n ) are identical. The master ( 10 ) likewise includes an identifier memory ( 22 ), in which the identifiers (a, b, . . . , d) of the slaves ( 12, 12   n ) are to be stored, so that the master can address the slaves ( 12, 12   n ) in a targeted way and can process the data output by the slaves ( 12, 12   n ). The processes according to the invention pertain to the storage of the identifiers (a, b, . . . , d) in the identifier memory ( 22 ) of the master ( 10 ) and to the procedure in the event of ai failure of slaves ( 12, 12   n ) and/or of the master ( 10 ), taking into account the case where no external computer ( 14 ) that could furnish all the required information is available. The device according to the invention and the processes according to the invention are especially suitable for use in a multiplexing system that is preferably disposed in a motor vehicle.

PRIOR ART

The invention is based on a device arrangement for exchanging data andon a process for operating such a device which generally includes a mainstation (master) and at least one secondary station (slave), which eachhave access via respective interfaces to at least one common data line.From European Patent Application EP-A 0 396 090, a generic device forexchanging data between a main station, called a master, and at leastone secondary station, called a slave, is known. Both the master and theslaves have interfaces, which each access at least one common data line.The master can address all the slaves. A data transmission from a slaveto the master that may possibly be necessary can be started by the slaveitself without being ordered to do so by the master. The essentialsignal processing is located in the master, while the slaves forinstance prepare the signals, output by sensors and supplied to theslaves, for data transmission to the master and optionally carry thesignals output by the master for actuating final control elements. Theseprovisions contribute to keeping the expense for circuitry in the slavesas low as possible, to enable inexpensive manufacture. The known deviceis contemplated in the context of a multiplexing system that is disposedin a motor vehicle. By way of example, the slaves are actuators fordevices relating to passenger comfort, control units and otherelectrical motor vehicle components that are controlled from a centralpoint by at least one master. The various slaves are embodieddifferently, so that they can meet the signal detection and signaloutput functions assigned to them.

The object of the invention is to provide a device for exchanging datathat can be made economically.

SUMMARY AND ADVANTAGES OF THE INVENTION

The above objects generally are achieved according to the presentinvention by a device or arrangement for exchanging data between a mainstation (master) and a plurality of secondary stations (slave), whicheach have access via respective interfaces to at least one common dataline, wherein: the master contains an identifier memory for receivingidentifiers of the slaves; the slaves are all substantially identicaland each contains one identifier memory in which an individualidentifier, which is unique to the associated slave and which is to bestored in the identifier memory of the master, is stored; and the slaveseach include one program memory for holding applications-specificprograms intended for the respective slave.

The device of the invention for exchanging data has the advantage thatall the secondary stations, hereinafter called slaves, are embodiedidentically, at least in a basic configuration. The various slavesdiffer only in an individual, one-time identifier, which is stored inthe slave in the form of a sequential serial number, for instance duringmanufacture. The functions to be performed by the slaves are notassigned to the slaves until after the device is put into operation. Thefunction of the slaves is defined by programs, which are stored in amemory for applications specific programs that is located in the slave.The main station, hereinafter called the master, contains an identifiermemory for holding the identifiers stored in memory in the slaves, toenable identifying the slaves.

A preferred application of the device of the invention is disclosed inthe context of a multiplexing system disposed for instance in a motorvehicle. One substantial advantage is the economical embodiment of thedevice of the invention, because a greater number of identical slavescan be manufactured. A further advantage arises in stocking of spareparts, which in the simplest case means uniformly embodied masters andthe identical slaves.

Advantageous further features and embodiments of the device of theinvention will become apparent from dependent device claims.

An especially advantageous provision is to equip the master with amemory for holding the applications-specific programs to be stored inthe slaves. If a replacement of a slave should become necessary in thecourse of a repair, access to the applications-specific programcontained in the master can be gained at any time, and it can be loadedin the new slave.

It is especially advantageous for each of the individual slaves to beassigned applications interfaces whose function is defined in accordancewith the applications-specific programs to be stored in the applicableslave. With this provision, it is possible to adapt the number of bothinputs and outputs to given requirements.

An advantageous embodiment provides that the identifier, stored ininvariable form in the various slaves and contained for instance in arandom access memory, is a sequential serial number assigned inproduction. This provision assures that if replacement of a slave shouldbecome necessary in a repair, the slaves will always have differentidentifiers.

An advantageous further feature provides that the master includes aninterface that makes it possible for the applications-specific programsto be stored in the various slaves to be loaded from an externalcomputer via the master into the slaves and into the memory that ispossibly present in the master. With this interface it is possible inparticular to transmit the identifiers of the various slaves to themaster.

The interface, by way of example, is a diagnostic interface inaccordance with DIN/ISO 9141. Embodying the interface as a standardizeddiagnostic interface enables self-diagnosis in the known device. Thememory required for the diagnostic data need be present only in themaster. The diagnostic data ascertained in the various slaves aretransmitted to the master via the common data line, and in the masterare either stored directly in the diagnosis memory or first are furtherprocessed in the context of diagnostic programs. The entire system ofmaster and slaves thus contains only a single diagnostic interface.

The processes of the invention each enable advantageous operation of thedevice of the invention.

In a first process of the invention, it is provided that the identifiersof the slaves are imparted to the master via the diagnostic interfacedisposed in the master. This provision thus directly makes theidentification process itself possible. The external computer alsofurnishes the applications-specific programs intended for the slaves.

In another process it is provided that the master procures theidentifiers stored in the various slaves on its own, by readout of theidentifiers stored in the slaves. The requisite for this process is thatthe slaves upon installation of the device of the invention areconnected to the common data line in a specified order and are put intooperation one after the other in that order. With this process, thereplacement of a defective master when the slaves are intact or thereplacement of at maximum all the slaves is possible.

Another process according to the invention for operating the device isdirected to repair, in which a slave is replaced. From a comparison ofthe identifiers stored in the master with the identifiers of the slavespresent before, the new slave can be ascertained, and the old identifierin the master replaced with the new identifier of the new slave.

Further advantageous features and embodiments of both the device of theinvention and the processes of the invention will become apparent fromthe further dependent claims and in conjunction with the ensuingdescription.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a device according to the invention for exchanging databetween a main station (master) and at least one secondary station(slave), and

FIGS. 2-4 show flow charts of processes for operating a device of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a main station 10, hereinafter called a master, which isconnected via an interface CAN with a data line 11, to which at leastone secondary station 12 a, 12 b, hereinafter called the slave, isconnected. The connection of the slaves 12 a, 12 b to the data line 11is effected via interfaces CAN, which are equivalent to the interfaceCAN provided in the master 10. The master 10 includes two furtherinterfaces. A first interface is a diagnostic interface 13, which can beconnected to an external computer 14 via two lines, marked K and L. Afurther interface contained in the master 10 is the master-applicationsinterface 15, which has a definable number of outputs 16 and inputs 17.

The control of the signal courses in the master 10 is performed by amicroprocessor 18, which cooperates with a random access memory 19, adiagnostic memory 20, a memory 21 for slave programs, and an identifiermemory 22. Both the memory 21 for slave programs and the identifiermemory 22 are divided into an equal number of memory spaces thatcorrespond to one another. The correspondence is indicated by connectinglines. Each of the memory spaces are marked a, b, . . . , d. The numberis fixed at n, which is equivalent to the maximum number of slaves 12,12 n that can be connected. For the sake of simplicity, the connectinglines in the master 10 that are present between the various componentsare not shown.

The master 10 is assigned a switch 23, for instance an already existingswitch in a dashboard, which is provided for the starting of events thatproceed within processes of the invention for operating the device,which processes will be described in detail hereinafter. The slaves 12,12 n are embodied identically. The number of slaves 12, 12 n that can beconnected to the data line 11 is limited to the number n. The slaves 12,12 n each include one microprocessor 24, 24 n, which cooperates with arandom access memory 25, 25 n, a memory 26, 26 n, and an identifiermemory 27, 27 n contained in the slave 12, 12 n. An individualidentifier for each slave 12, 12 n is stored in the identifier memories27, 27 n, respectively, and is shown in the exemplary embodimentillustrated as a, b, . . . , d. The various slaves 12, 12 n differ fromone another only in this identifier a, b, . . . , d. In addition to theinterface CAN, each slave 12, 12 n includes a slave-applicationsinterface 28, 28 n, whose function, however, can be programmeddifferently from slave to slave, 12, 12 n. The slave-applicationsinterface 28 in the slave 12 includes a predeterminable number ofoutputs 29 and a predeterminable number of inputs 30. Theslave-applications interface 28 n in the slave 12 n includes a likewisepredeterminable number of outputs 30 and a predeterminable number ofinputs 32.

The device of the invention functions as follows:

The master 10 and the at least one slave 12, 12 n, which can eachexchange data over the same interfaces CAN and over the common data line11, are located for instance in a motor vehicle in the framework of amultiplexing system. Both the master 10 and the slaves 12, 12 ncooperate with control units, actuators or sensors. Certain actuatorsand sensors can be combined into a function unit to which a respectiveslave 12, 12 n is assigned. Such a functional unit is, for example, anadjuster relating to passenger comfort, disposed in a motor vehicle dooror seat. Examples of actuators provided in such adjusters are electricmotors, valves, lamps and the like, while rpm sensors or positionsensors are present as the sensors. Actuators may be connected directlyto the outputs 16 of the master 10, the outputs 29 of the slave 12, orthe outputs 31 of the slave 12 n, optionally with the interposition ofan end stage. The sensors may be connected directly to the inputs 17 ofthe master 10, the inputs 30 of the slave 12, or the inputs 32 of theslave 12 n. In the other embodiment already mentioned, the master 10 orone of the slaves 12, 12 n can cooperate with a control unit; therequired data exchange likewise takes place via the applicationsinterfaces 15, 28, 28 n. The terms “master” and “slave” do not have themeaning that only the master 10 can start a data transmission orpurposefully call up a slave 12, 12 n. On the contrary, multimasteroperation is possible, in which all the participants 10, 12, 12 nconnected to the common data line 11 can start a data transmissiondirected to an arbitrary other participant 10, 12, 12 n. Collisions canbe averted with a list of priorities.

One substantial advantage of the device of the invention is that theslaves 12, 12 n, at least in the basic configuration, are embodiedidentically. This provision favors economical mass production and simplestockkeeping. The various slaves 12, 12 n differ solely in theidentifier 27, 27 n, which by way of example is an individual, unique,sequential serial number that can be programmed into the respectiveidentifier memories 27, 27 n of the slaves 12, 12 n in a concludingfunction check at the end of the production line. The identifier memory27, 27 n can be considered part of the random access memory 25, 25 ncontained in the slave 12, 12 n; this memory likewise contains data thatare stored in production, and the data contained in the random accessmemory 25, 25 n are identical for each slave 12, 12 n. The data storedin the random access memory 25, 25 n may be assigned to differentprograms. For instance, one program supports the work of the interfaceCAN, while the other program carries out diagnosis of the outputs 29, 31and the inputs 30, 32, for instance. The diagnosis detects shortcircuits, interruptions and overloads, for instance, and can optionallycarry out plausibility observations, which are required to detect errorsthat do not amount to a total failure. The diagnosis is especiallyvaluable for detecting sporadic errors. The data ascertained by thediagnostic program are stored in the memory 26, 26 n. The memory 26, 26n is a memory type (EEPROM) that is electrically writable and preferablyis also electrically eraseable.

The essential task of the memories 26, 26 n contained in the slaves 12,12 n is the storage of applications-specific programs. Anapplications-specific program for instance defines the number of outputs29, 31 and the number of inputs 30, 32. It is also possible to definewhether the outputs 29, 31 and the inputs 30, 31 function digitally orin analog fashion. Moreover, one applications-specific program eachshould be stored that is capable of controlling the function unitconnected to the respective slave 12, 12 n and can optionally furtherprocess reports back from it.

The applications-specific programs initially not contained in the slaves12, 12 n, which are to be stored in the memory 26, 26 n, are loaded fromthe master into the memories 26, 26 n of the slaves 12, 12 n via thedata line 11 when the applicable slave 12, 12 n is put into operation.For carrying out this task, it is essential that the master 10 know theidentifier a, b, . . . , d of the various slaves 12, 12 n connected tothe data line 11, so that an unambiguous assignment of the programs forthe slaves 12, 12 n is possible. The identifier a, b, . . . , d of theslaves 12, 12 n is stored in the identifier memory 22 of the master 10.The various identifiers a, b, . . . , d can be imparted to the master 10either by the slaves 12, 12 n themselves or by the external computer 14.The external computer 12, 14 communicates with the master 10 via thediagnostic lines K, L connected to the diagnostic interface 13.

The designations K, L establish a connection in conformity with theDIN/ISO Standard 9141, to which reference is hereby expressly made.Although DIN/ISO 9141 is directed to the diagnosis of electronic systemsdisposed in the motor vehicle, a more-extensive data transmission, forinstance including the storage of the individual identifiers a, b, . . ., d in the identifier memory 22 may readily be contemplated as well.According to DIN/ISO 9141, at least one line K is required. The externalcomputer 14 contains the diagnostic test unit, named in DIN/ISO 9141,which performs the diagnosis. The diagnostic data, which are eitherascertained by the master 10 itself or transmitted to the master 10 bythe individual slaves 12, 12 n, are stored in the diagnosis memory 20.The master 10 can process the diagnostic data output by the individualslaves 12, 12 n and, for instance by comparison of the diagnostic dataoutput by various slaves 12, 12 n, can detect errors that have not beendetected in the individual slaves 12, 12 n. The diagnostic data storedin the diagnosis memory 20 can be interrogated and/or cancelled by theexternal computer 14 in accordance with DIN/ISO 9141. The diagnosismemory 20 in the master 10 is preferably also equivalent to a memorytype (EEPROM) that is electrically writable and eraseable. Instead ofthe external computer 14, naturally any other suitable diagnosis unitcan also be used.

The diagnosis memory 20 in the master 10 may optionally have a memoryregion that receives applications-specific programs that the master 10requires, if there is a master-applications interface 15. Themaster-applications interface 15 makes it possible for the master 10, inaddition to its other tasks, to take on a function that is alsoperceived by the slaves 12, 12 n. The applications-specific programsoptionally stored in the diagnosis memory 20 therefore define both thenumber of outputs 16 and inputs 17 and their function, for instancewhether they are digital or analog.

The programs determined for the various slaves 12, 12 n and to be storedin the memories 26, 26 n of the slaves 12, 12 n may in one embodiment betransmitted from the external computer 14 into the master 10 and carriedonward by the master 10. In an especially advantageous further featureof the device according to the invention, it is contemplated that thememory 21 for slave programs, in which the programs to be stored in thevarious slaves 12, 12 a are also stored, is provided in the master 10.With this provision it is possible, if the device of the inventionfails, for instance in the event of a defect of one or more slaves 12,12 n or a failure of the master l0, to perform a repair even without anexternal computer 14. Without the external computer 14, initializationcan be started with the switch 23.

The various processes for operating the device of the invention will bedescribed in further detail below in conjunction with the flowchartsshown in FIGS. 2-4:

FIG. 2 shows a flowchart that corresponds to a process by which thedevice of the invention can be put into operation, in which theidentifiers a, b, . . . , d of the slaves 12, 12 n to be stored in themaster 10 and the applications-specific programs each to be stored inthe slaves 12, 12 n are furnished by the external computer 14 in thememory 26, 26 n. The identifiers a; b, . . . , d of the various slaves12, 12 n are known to the external computer 14. This information can beinput manually, for instance, by reading out the identifiers a, b, . . ., d, which by way of example are either printed directly on theindividual slaves 12, 12 n or are printed on a package of slaves 12, 12n.

After a start 40 tripped by the external computer 14, in an assignmentstep 41 a counting variable z is set equal to the number n of slaves 12,12 n. In an ensuing memory step 42, the identifier a of the first slave12 is stored in the identifier memory 22 in the master 10. In the nextmemory step 43, the program furnished by the external computer 14 isloaded via the master 10, the interfaces CAN and the common data line 11into the memory 26, 26 n of whichever slave 12, 12 n has an address orpart thereof that corresponds to the identifier a, b, . . . , d. Theprerequisite is that the association of the variousapplications-specific programs with the identifiers a, b, . . . , d beknown to the external computer 14. Since the individualapplications-specific programs are defined, care must merely be takenthat the applicable slave 12, 12 n is brought to the specified placewhere the applicable applications-specific program is to run. In thenext memory step 44, it is provided that the applications-specificprogram stored in the respective slave 12, 12 n is also memorized in thememory 21 for slave programs, if the memory 21 is provided in the master10. This is why the memory step 44 is shown in dashed lines in FIG. 2.In an ensuing assignment step 45, the value of the counting variable zis reduced by one. The ensuing interrogation step 46 finds out whetherall the slaves 12, 12 n have been accounted for. If not, a return tomemory step 42 is made. If so, the initialization is at an end. Afterthe end of the initialization, normal operation begins.

If one slave 12, 12 n fails, the affected slave 12, 12 n is replaced. Ifthe external computer 14 is available, then the master 10 need merely betold the new identifier a, b, . . . , d of the new slave 12, 12 n andstorage of the applications-specific programs in the affected memory 26,26 n brought about. If the external computer 14 is not available, thenif one slave 12, 12 n fails the process according to the invention asshown in FIG. 3 is provided; the prerequisite is that the memory 21 forslave programs be present in the master 10, and that the individualslaves 12, 12 n are capable of transmitting their identifier a, b, . . ., d to the master 10; the various identifiers a, b, . . . , d of theslaves 12, 12 n must be known in the master 10. Accordingly, a generaladdressing of the slaves 12, 12 n, in which all the slaves 12, 12 nconsider themselves to have been addressed, without sending theidentifier a, b, . . . , d as part of the address, must be possible.

After a start 50, which can be tripped with the switch 23, for instance,in the assignment step 51 the counting variable z is assigned a valuethat is equivalent to the number n of slaves 12, 12 n. In an ensuinggeneral transmission request 52, the master 10 elicits a response fromeach slave 12, 12 n. In a read-in operation 53, the applicableidentifier a, b, . . . , d of a slave 12, 12 n that has just nowresponded is read into the master 10 and optionally compared immediatelywith the identifiers a, b, . . . , d of the slaves 12, 12 n stored inthe identifier memory 22 of the master 10. In the ensuing interrogationstep 54, it is ascertained whether all the slaves 12, 12 n have alreadyanswered. If not, then in an assignment step 55 the counting variable isreduced by one and a return to the read-in operation 53 is made. Thefunctionally capable slaves 12, 12 n are configured and respond with aspecial message, which preferably directly contains the identifier a, b,. . . , d of the applicable slave 12, 12 n. A message priority list foraccess to the bus, which list is stored in the slave 12, 12 n, preventsa data collision on the data line 11. Only the one slave 12, 12 n thathas been replaced answers with a general message, which the master 10can interpret accordingly. The replaced slave 12, 12 n is thusidentified. If it is found in the interrogation step 54 that all theslaves 12, 12 n have been accounted for, then in the assignment step 56an initialization of the new slave 12, 12 n takes place, by transmissionof the applications-specific program, provided for the applicable slave12, 12 n, that is stored at the appropriate point in the master 10 inthe memory 21 for slave programs. Simultaneously, in the master 10, theidentifier a, b, . . . , d of the new slave 12, 12 n that has been readin is transmitted to the identifier memory 22 at the appropriate point,and the former identifier a, b, . . . , d of the already replaceddefective slave 12, 12 n first having been deleted.

A further process according to the invention pertains to the procedurein the event of failure of the master 10. With the prerequisite that allthe slaves 12, 12 n are functioning properly and therefore know theparticular applications-specific program assigned to them, the memory 21for slave programs is not necessary in the master 10. If this memory 21for slave programs is present and contains the correspondingapplications-specific programs provided for the various slaves 12, 12 n,then not only the master 10 but in addition an arbitrary number ofdefective slaves 12, 12 n can be replaced. The process of the inventionwill be described in further detail in conjunction with the flowchart ofFIG. 4. After a start 60, which ensues for instance by turning on theenergy supply of the replaced master 10 or for instance after analready-tripped test course, first in an assignment step 61 a countingvariable z is assigned the value n, which is equivalent to the number ofslaves 12, 12 n, which number must be known to the master 10. The numbern is equivalent to the memory spaces for the various identifiers a, b, .. . , d in the identifier memory 22. For the ensuing process theprerequisite must be that the slaves 12, 12 n be connected successivelyto the common data line 11 in a specified order. If a plurality ofdefective slaves 12, 12 n are to be replaced, then in this case as wella specified order of connection must be adhered to. The orderexpediently corresponds to the numbering of the slaves 12, 12 n, whichis equivalent to the current status of the counting variable z. In thenext step 62, a slave 12, 12n is to be connected to the common data line11, and the order must be adhered to. After the affected slave 12, 12 nis connected, the master 10 must be informed that the connectionoperation has been completed. This is done in the program step 63 forinstance by an actuation of the switch 23. The switch actuation causesthe master 10 to transmit a general interrogation 64, which causes thenewly connected slave 12, 12 n to output its identifier a, b, . . . , dstored in the identifier memory 27, 27 n. The further course of theprocess depends on whether the memory 21 for slave programs is presentin the master 10, and whether the applications-specific programs for thevarious slaves 12, 12 n are stored in it. If this memory for slaveprograms 21 is not present, then defective slaves 12, 12 n cannot bereplaced. The course of the process proceeds directly to the assignmentstep 66, which performs a reduction of the counting variable z by one.Conversely, if the memory 21 for slave programs is present in the master10, then after the output 65 of the identifier a, b, . . . , d, twooptions are possible in the ensuing step 67. If the memory 21 for slaveprograms is present but contains no applications-specific programs, thenthe applications-specific program must be present in each slave 12, 12n. In step 67, a transmission of the applications-specific programcontained in the applications-specific memory 26, 26 n to the master 10is performed, and this program is placed there at a memory space of thememory 21 for slave programs that is equivalent to the sequentiallycounting variable z and to which the applicable identifier.a, b, . . . ,d is assigned. With this provision it becomes possible to handle afailure of a slave 12, 12 n occurring at some later time by simplyreplacing the affected slave 12, 12 n; the applications-specificprograms to be stored in the affected slave 12, 12 n can be called up bythe master 10. If the memory for slave programs 21 is present in themaster 10 and contains the various applications-specific programs, thenin step 67 the appropriate applications-specific program can be madeavailable the last slave 12, 12 n to be connected to the common dataline 11. With this provision, a replacement of the affected slave 12, 12n is possible. After the assignment step 66, it is found out that in theinterrogation step 68 whether all the slaves 12, 12 n have beenaccounted for. If not, then the next slave 12, 12 n is connected to thecommon data line 11 in step 62, and the general interrogation 64 isbegun with step 63. Conversely, if in the interrogation step 68 it isfound that all the slaves 12, 12 n have been accounted for, then theinitialization is complete.

What is claimed is:
 1. An arrangement for exchanging data between a main station (master) and a plurality of secondary stations (slave), which each have access via respective interfaces to at least one common data line, wherein the master contains an identifier memory for receiving and storing identifiers of the respective slaves; the slaves are all substantially identical and each contains one identifier memory, in which an individual identifier, which is unique to the associated slave and which is to be stored in the identifier memory of the master, is stored; and the slaves each include one program memory for holding applications-specific programs intended for the respective slave.
 2. The arrangement of claim 1, wherein the master, a memory is provided for holding the application-specific programs to be stored in the respective slaves.
 3. The arrangement of claim 2, further comprising means for, following replacement of a slave with a new slave, causing a replacement of the identifier stored in the identifier memory of the master for the replaced slave, with a new identifier of the new slave, and for causing a transmission of the applications-specific programs, contained in the memory for slave programs in the master to the new slave and the storage of the application-specific programs in the program memory of the new slave.
 4. The arrangement of claim 1, wherein the function of a slave-applications interface contained in a respective slave is defined by an applications-specific program stored n the program memory of the respective slave.
 5. The arrangement of claim 1, wherein the individual identifier stored in the respective slaves is a sequential number (serial number) assigned during the manufacture of the slaves.
 6. The arrangement of claim 1, wherein a diagnosis memory for storing diagnostic data of the slaves and/or diagnostic data of the master is provided in the master, which diagnostic memory can be read out and erased by an external computer via a diagnostic interface disposed in the master.
 7. The arrangement of claim 1, wherein the applications-specific programs to be stored in the respective program memory of each of the slaves are furnished by an external computer, which can be connected to the master via a diagnostic interface contained in the master.
 8. The arrangement of claim 6, wherein the external computer loads the identifiers of the slaves to be stored in the master into the identifier memory contained in the master, and the external computer loads the applications-specific programs, to be stored in the slaves in the respective program memory of each of the slaves via the master.
 9. The arrangement of claim 1, wherein slaves interrogate the identifiers of the slaves that are to be stored in the identifier memory of the master, and the slaves are connected in succession to the common data line in a specified order.
 10. The arrangement of claim 1, wherein the arrangement is part of a time-division multiplexing system, preferably disposed in a motor vehicle, whereby a data exchange between the master and the slaves or among the slaves takes place by time division multiplexing over the common data line. 